One of the main problems in the design of isolator blades is to provide a structure that can resist the applied loadings due to gas pressure, weight and seal loading, and will also not distort under start-up/shut down temperature transients as well as steady state elevated temperature operating conditions.
In the usual construction the blade assembly consists of a blade arm frame with individual blades attached to it, one for flap isolators, two for diverter valves, the attachment being carried out in such a way that differential movements are possible between the blades and blade arm frame.
A known blade structure is shown in FIG. 1 of the accompanying drawings, which is an exploded isometric view of a known type of blade structure of a diverter isolator, and which shows a blade arm frame 1, to one side of which is attached a boiler inlet blade 2 to which is in turn attached an insulation 3 and an insulation cladding 4. To the other side of the blade arm frame 1 is attached a bypass blade 5 to which is in turn attached another insulation 6 and an insulation cladding 7. The blade arm frame 1 itself has a central fixing 8 for the blades and blade location guides 9.
The operating shaft comprises a connecting shaft 10 and, at each end thereof, a stub shaft 11 having a keyed and bolted flange connection 12, a shaft seal 13, a high temperature shaft bearing 14, a coupling 15, and an actuator 16. The actuator 16 has a motor 17, a reduction gear box 18 and bevel gearing 19. There is also a hand wheel 20. It may be noted that the drive motor assembly can be mounted centrally or inboard of actuators over duct as site conditions allow.
Details of the blade structure shown in FIG. 1 are illustrated in FIGS. 2a-2d of the drawings, wherein FIG. 2a is a perspective view of the assembled blade structure, and FIGS. 2b, 2c and 2d are detailed perspective views showing the areas indicated A, B and C respectively in FIG. 2a. Specifically FIG. 2b shows a clamp arrangement between the various parts of the blade structure, and in particular illustrates the insulation infill 3 and 6, FIG. 2c shows the centre location pin structure, and FIG. 2d shows the guide key structure.
The disadvantage of this type of structure is that overall blade weight is high, leading to high operating torques.